1. Field of the Invention
The present invention relates to a method for producing an adhesive material for medical applications, such as a dressing, and the material thus produced.
2. Description of the Related Art
There are currently different types of adhesive materials used to treat wounds (dressing components, protective adhesive films) and/or to use for maintaining compresses or medical devices (adhesive tapes, patches) designed for atraumatic contact with healthy skin and the wound.
Typically, such adhesive materials are obtained by different methods for depositing an adhesive on a receiving substrate.
Thus, for example known is a method for direct coating of the adhesive on the receiving substrate, followed by heat treatment of the adhesive (drying or cross-linking) and the placement of a protector (liner) on the adhesive face of the obtained material. Typically, the receiving substrate may be subject to coating with an adhesion primer or a corona treatment intended to favor the adhesion between the substrate and the adhesive.
However, this method may only be applied to substrates:                that are thermally compatible (no melting, softening or shrinkage), and        that have a low porosity opposing the crossing of silicone through the substrate during the coating.        
This method often requires a prior, therefore costly, step for depositing an adhesion primer layer. As a result, this method is very limiting in terms of materials that can be produced and may have an excess production cost.
According to one known alternative embodiment, the adhesive is coated onto a film treated with an anti-adherent for the adhesive, then a lining operation is followed by calendaring of the receiving substrate on the adhesive before performing a heat treatment of the assembly (drying or cross-linking).
Nevertheless, this method requires receiving substrates:                that are thermally compatible (no melting, softening and/or shrinkage) with going through the cross-linking step of the silicone,        having a limited porosity and/or capillarity opposing the crossing and/or absorption of the adhesive through and/or by the receiving substrate during the time between the lining of the substrate on the adhesive in liquid state and the cross-linking of the adhesive, and        having a roughness or a fibrous surface allowing anchoring of the piece when a prior step for depositing a primer must be avoided.        
This method often requires a prior, therefore costly, step for depositing an adhesion primer layer because the fusion between the silicone and the substrate may not be sufficient for the application, even with corona treatment of the substrate before coating.
As a result, this method is less limited in terms of materials that can be produced than the previous one, but also has an excess production cost.
According to a final embodiment, the adhesive is coated on a film treated with an anti-adherent for that adhesive, the adhesive is heat treated (drying or cross-linking), then a lining operation is done, followed by calendaring of the receiving substrate on the adhesive face. As a general rule, the receiving substrate is subject to a corona treatment intended to favor adhesion between the substrate and the adhesive.
This method should make it possible to open up possibilities for substrates intended for heat-sensitive uses (subject to melting, softening and/or shrinkage) and porous supports, since these substrates are applied on the adhesive without the substrates going through a cross-linking furnace on a still-liquid adhesive.
However, given the very low surface energy of silicone adhesives, such a method is applicable (or applicable in a very limited manner to certain substrates) because the adhesion force between the substrate and the silicone in cross-linked state is very weak, even if the substrate has undergone a prior corona treatment.
As a result, the obtained products:                for the large majority, are not industrially feasible: the adhesion between the silicone adhesive and the release process liner is greater than the adhesion between the silicone adhesive and the receiving substrate, which implies that the transfer of the adhesive mass is not occurring; and        can, in some cases, be industrially possible to produce, but have prohibitive weaknesses if the adhesion between the silicone adhesive and the patient's skin is greater than the adhesion between the silicone adhesive and the receiving substrate, which implies a malfunction of the medical device and/or unacceptable adhesive residues on the patient's skin.        
Furthermore, in the general industrial field, and more particularly in the dressing and medical device industry, insufficient adhesion between a given adhesive and a material to be glued can be strengthened by corona treatment of the material to be glued.
Thus, for example, when a compress is deposited on a dressing having a base of a support coated with acrylic adhesive, better holding of the compress (whether dry or filled with water) is obtained via corona treatment of the face of the compress intended for gluing.
This works very well for acrylic adhesive and a large number of materials to be assembled or glued. However, this is not the case for a silicone adhesive for which a corona treatment applied to the materials to be assembled or glued does not yield satisfactory results due to the low surface energy of said silicone adhesive.
For example, in the case of an absorbent dressing compress, a low adhesion will be obtained when the compress is saturated with aqueous exudates from the wound. Silicone being hydrophobic by nature, there will no longer be any adhesion between the compress and the adhesive. It will then be difficult to remove the dressing because the layers of the dressing will separate from one another.
Thus, all of the known and previously described methods and materials have limitations.
One aim of the present invention is therefore to resolve the aforementioned problems, using an easy-to-implement and inexpensive solution that is optimized in terms of effectiveness, reliability, durability and quality of the obtained result.